By a heat recoverable article is meant an article whose dimensional configuration may be made to change when subjected to appropriate treatment. Usually these articles recover to an original shape from which they have previously been deformed, but the term "recoverable", as used herein, also includes an article which adopts a new configuration, even if it has not been previously deformed.
Heat recoverable articles which are based on fabrics are described in the following patent publications and copending applications: U.S. Pat. No. 3669157 (Carolina Narrow Fabric), European patent application publication Nos. 0116393 (MP0790), 0116391 (RK169), 0117026 (RK176), 0115905 (RK177), 0116392 (RK178), 0116390 (RK179), 0117025 (RK181), 0118260 (RK189), 0137648 (RK205), 0153823 (RK228), 0175554 (RK246), European patent application No. 86303767.7 (RK273), British patent application Nos. 8528966 (RK289), 8610813 (RK296), 8529800 (B118) and U.S. patent application No. 821662 (B121). The disclosure of those applications are incorporated herein by reference. The manufacture of heat recoverable articles from fabrics containing heat recoverable fibres has a number of advantages as compared with conventional heat-shrinkable products including ease of manufacture, since no subsequent expansion step is necessary, improved mechanical properties such as tensile strength, abrasion resistance and split resistance, and the ability to introduce very high strength heat stable fibres into the articles, all of which enable heat recoverable fabrics to be employed in fields hitherto considered inappropriate for heat shrinkable products.
Europeant patent application No. 0175554 (RK246) describes a heat recoverable fabric which can be used for electrical screening. For such an application the fabric comprises conductive fibres, or fibres coated with a conductive material. Aluminium coating is preferred, but a conductive polymer coating may also be used.
The heat recoverable fabrics described in the prior art have many applications, for example covering, mechanically protecting, electrically screening, and environmentally sealing objects enclosed by the fabric. For many of those applications it is particularly desirable for the fabric to provide an enclosure which is impervious to the ingress of water, moisture or other liquid. An example of such an application is where the fabric is to provide an enclosure for a splice between electrical cables for example telecommunication cables. In such applications, presence of water may cause an electrical short circuit, and consequent signal distortion. In the heat recoverable fabric materials described in the prior art imperviousness is typically achieved by using a polymeric material in conjunction with, bonded to, or extending throughout the recoverable fabric. That polymeric material is typically applied as a laminate layer on one or both sides of the fabric, or as a matrix through which the fibre extends. The prior art fabrics preferably have finite thickness of polymeric material on each side of the fabric.